This invention relates generally to magnetic sheet apparatus and to teaching apparatus. More specifically the invention is directed to improvements in a magnetic sheet player, with or without provisions for recording, in which the recording medium takes the form of what is herein termed a magnetic sheet, that is, a rectangular sheet of paper or other material with a spiral magnetic track on one surface and with characters, pictures, tables or the like printed on the other surface by way of visual presentation of the subject of audio information prerecorded on the track. The machine of this character is employed extensively for audiovisual teaching purposes, although it is adaptable for other applications as well within the scope of this invention.
In magnetic sheet players under consideration the magnetic sheet to be played back or recorded on is stationarily mounted in position on the machine, with its track-bearing surface directed downwardly, and a movable magnetic head under the sheet follows its spiral track by travelling along a radial guide slot in a turntable in step with its rotation. Heretofore the magnetic sheet has usually been secured to the machine by means of a rigid cover plate that covers the entire surface of the sheet under pressure, with the magnetic head resiliently urged into abutting contact with the sheet.
The use of the rigid cover plate according to the prior art is objectionable because it prevents the magnetic sheet from making as intimate contact with the magnetic head as, for example, the usual magnetic tape in a magnetic recorder or reproducer. The conventional cover plate is also insufficient for holding the magnetic sheet in position against any possibility of displacement, with its track in precise registration with the air gap in the magnetic head.
Another disadvantage with the prior art arises from the upright disposition of the magnetic head with respect to the horizontally supported magnetic sheet. As the magnetic head travels along the spiral track on the magnetic sheet, it encounters substantial frictional resistance which can cause the head to incline in the direction away from its direction of travel, thereby impairing the desired neat contact with the sheet.
The poor or improper contact of the magnetic head with the magnetic sheet can deteriorate the playback quality to such an extent that the machine is only capable of reproducing speech with a tolerable degree of fidelity but is quite inadequate for reproduction of music or the like of listenable quality. The machine with such inferior playback quality if unsuitable for language study, either, where the exact pronunciation, accentuation and intonation of the speaker must be reproduced. Proper contact between head and sheet is a prerequisite for sound reproduction over as wide a range of frequencies as is possible with the machine.